This invention relates generally to a crop residue chopper for an agricultural combine, and more particularly to a chopper for receiving crop residue, primarily straw, stalks, and other plant material, from threshing mechanism of the combine, and chopping the residue and propelling it outwardly from the combine, the chopper utilizing a rotatable rotor having knives fixedly mountable thereon in alternative configurations for finely chopping the residue, or more coarsely chopping the residue, as desired.
Due to the differences in farming practices and preferences, some farmers and operators require or desire straw and other crop residue discharged from the threshing mechanism of a combine to be cut or chopped very finely, while others prefer the residue to be more coarsely cut or chopped. It is well known to provide a chopper on a combine for receiving crop residue output from the threshing or separating mechanism of the combine. Typically, such choppers include a rotatable rotor supporting a plurality of knives for rotation therewith, which knives pass between a plurality of stationary knives for cutting or chopping the crop residue received as the rotor is rotated. To produce coarser cut crop residue, the knives on the rotor are typically fixedly mounted thereon, and are in a one-to-one ratio to the stationary knives. For a finer cut, pivotable flail type knives are typically used on the rotor, in a ratio of two-to-one to the stationary knives. A disadvantage, however, of a flail knife rotor compared to a fixed knife rotor is the additional cost for the pivotal mounting apparatus for the knives, such as bushings, bearings or the like. It has also been found that flail knife rotors tend to be less reliable than fixed knife rotors due to problems relating to wear of the pivoting components. Flail knives has also been known to produce more vibration than fixed knives, when rotated. Still further, due to the differences between flail knife and fixed knife constructions, providing a rotor configured to alternatively use both for providing a fine cutting capability and a coarse cutting capability has been found to be undesirably costly.
Therefore, what is sought is a crop residue chopper for an agricultural combine which can be alternatively configured for finely and coarsely chopping crop residue utilizing only fixed knives on the rotatable rotor thereof, so as to be less costly, more reliable, and produce less vibration than known constructions using flail knives.
According to the present invention, a rotor for a crop residue chopper for an agricultural combine for rotation about a rotational axis extending through the rotor adjacent to an axially spaced array of stationary knives of the chopper, which provides many of the above sought features, is disclosed. The present rotor preferably includes a plurality of mounting elements supported in predetermined axially spaced relation one relative to another, and a plurality of offset knives, each of the offset knives including a mounting end portion fixedly mountable on one of the mounting elements and a free end portion opposite the mounting end portion disposed so as to extend radially outwardly in axially offset relation to the mounting end portion when mounted on the mounting element, the offset knives being mountable in-pairs on the mounting elements in a predetermined fine chopping configuration wherein the free end portions of the knives of each of the pairs are offset in a predetermined first relation to the mounting ends thereof, respectively, and define a space between the free end portions having a predetermined first axial extent so as to be capable of passing on opposite sides of predetermined ones of the stationary knives and performing a cutting function in cooperation therewith when the rotor is rotated, and selected ones of the offset knives being mountable singly on the mounting elements in a predetermined coarse chopping configuration with the free end portions of the selected ones of the knives offset in an opposite direction from when in the fine chopping configuration so as to define axial spaces between adjacent ones of the free end portions having a predetermined second axial extent greater than the first axial extent for passage in proximity to predetermined ones of the stationary knives for performing a cutting function in cooperation therewith when the rotor is rotated.
Preferably, when in the fine chopping configuration, the free end portions of the offset knives of each pair extend radially outwardly in diverging relation, such that when handling larger, harder items of crop residue, such as corn cobs, the cobs will not have a tendency to become lodged between the knives. In the coarse chopping configuration, preferably alternating ones of the stationary knives are removed.